Separating non-acids from soap stocks



nited States SEPARATING N ON -ACIDS FROM SOAP STOCKS I Richard R. Chaseand John C. Bowers, Savannah, Ga.,

assignors to Union Bag-Camp Paper Corporation, New York, N. Y., acorporation of Virginia Application `luly 11, 1956, Serial No. 597,265

2 Claims. (Cl. 26o-97.7)

by removing the undesirable unsaponiables, thus making the resultingproduct more valuable.

Another object of the invention is to provide a processy for obtaining anon-acid fraction, rich in sterols and other valuable constituents suchas lignoceryl and other higher alcohols. Production of rened sterols oralcohols from this non-acid fraction may be accomplished by any of anumber of well known methods. In the case of sterols, the purificationmay be by acid precipitation and crystallization.

Previous solvent separations of the non-acids from soap stocks haveinvolved either extraction of dry soap or extraction of aqueoussolutions of soaps. When dry soaps are used, an expensive dryingoperation followed by a difficult so-lid-liquid extraction makes theseparations uneconomical. When aqueous solutions were used, as in U. S.Patent No. 2,530,809, it has always been necesT sary to use substantialquantities of a material such as low molecular weight alcohols withinthe solution to prevent emulsions. We have discovered that esters of arelatively low molecular weight aliphatic acid and a relatively lowmolecular weight alcohol can be used as extraction solvents for aqueoussoap solutions without need for further materials to prevent emulsions.Itis therefore a further object of the invention to provide a processwhich greatlysimplifies the prior economically unattractive process andis a distinct improvement over it.

A further object of the invention is to provide a process which issimple, efficient and economical to operate.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises the several steps and the relatio-nof one or more of such steps with respect to each of the others thereof,which will be exemplified in the process hereinafter disclosed, and thescope of the invention will be indicated in the claims.

In our process the separation is effected by countercurrent extractionof soap or soap material with a solvent. In the practice of thisprocess, the following steps are employed:

(l) The soap may be dissolved in water to give a homogeneous mixture. Inthe event the starting material is not in soap form, it is tirstnecessary to convert it to a soap by any of several processes, forexample, by boiling with caustic soda solution. We have found that a,dilution of the soap with one to two parts of water is atent O ICCsatisfactory. Although there is no reason why more or less water may notbe used successfully, if desired, it should be pointed out that thelower limit is governed by the requirement that sufficient water mustbeadded to put all the soap in solution. With regard to the upper limit,additional amounts of water above those specified may be added, butlarge quantities will make the process uneconomical because of thenecessity for handling an excessively large quantity of material, thusincreasing both equipment costs and operating costs.

(2) The above aqueous solution of soap is subjected to extraction withthe ester solvent. This may be done by any one of several methods, butcountercurrent extraction is probably the most eicient. So far ourextractions have been made in separatory tunnels, in a Podbielniakcentrifugal extractor or in a mixer-settler extraction apparatus,although other extraction devices such as packed columns can also beused.

(3) The solution of unsaponiable material extracted from the soap may bewashed with Water to free it from traces of the soap carried over. Thiswater may then be used in making the original soap solution if desired.This washing step is not essential.

(4) The solutionof unsaponiables is freed of solvent by evaporatng andstripping. 1 (5) The extracted unsaponifiable material may be furtherprocessed to remove the sterols present by any of a number of methodssuch as crystallization from suitable solvents, acid refining, orfurther extraction with solvents as disclosed by Vogel and Christensenin U. S. Patent No. 2,499,430.

(6) The soaps of fatty and rosin acids which have Vbeen materiallyreduced in non-acid content by this process may be recovered in anyconvenient manner such as salting out or converting to oils. In mostcases it would first be preferable to remove residual ester solvent byevaporation. Conversion to oils could then be made by treating withacids such as hydrochloricv or sulfuric. The resulting product whichseparates from the aqueous phase may be skimmed oi and is a distinctimprovement over the starting material.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawing, in which the single figureshows a diagrammatical flow sheet and the arrangement of apparatussuitable for carrying out the invention.

Referring more particularly to the drawing, it will be seen that theapparatus .comprises an extractor which consists of a single column forextracting and washing the unsaponiable extract. It will be recognizedthat two columns or other extraction devices could be used equally wellor that the washing step could be omitted if desired. The solvent entersthe bottom of the extraction zone at 1 and flows up the columncountercurrent to the soap solution, leaving at 2 after having extractedthe non-acids and having been washed relatively free of both entrainedand dissolved soaps. Water enters the top of the washing zone at 3 andfalls through the rising solvent Washing out the soaps. In theclaritication zone the water separates from the rising solvent and isdrawn off at 4. This water containing soaps is mixed with the feed stockat 5 and the resulting soap solution enters the top of the extractionzone at 6. The soap solution falls through the extraction zone leavingthe column at 7. The nonacids are freed of solvent in the still at 8,the recovered solvent 9 being returned to the bottom of the extractionzone at 1. The non-acids are withdrawn from the still to lstorage 10.The soaps leaving the column at 7 Vare stripped in still 11 of solventand a portion of water in which the soaps are dissolved. Thesolvent isseparated from the distilled water in decanter 12 and returned, togetherwith the solvent produced in still 8, to the extraction zone at 1. Thewater from the decanter 13 will be saturated with solvent and forconvenient recovery of this solvent it is returned to the column at 3 aspart of the wash water. The solvent-free aqueous soap solution isremoved from still 11 to aciditier `14. Here acid is added to convertthe soaps to oils. It might be desirable to add all or part of the acidbefore stripping off the ester solvent in still 11 since addition of theacid at this earlier point would reduce foaming tendencies in thisstripping operation. Two liquid phases are formed upon thisacidification andthe oil phase is removed to storage while the aqueousphase containing salts in solution is discarded, processed for recoveryof its chemical content, or otherwise disposed of. The relatively smallamount of solid phase that is formed may be discarded.

The foregoing arrangement of apparatus and ow sheet are given forpurpose of illustration. It will oe recognized that numerous variationsof this apparatus may be used without departing from the spirit of theinvention. The following specific examples will illustrate the practiceof the invention. These are considered examples only and by no means`are intended to limit the extent of the materials used or `themodifications possible.

Example I As an example of our invention, 25 pounds of black liquorskimmings were dissolved in 50 pounds of water. The resulting mixturewas pumped into the center of a Podbielniak centrifugal extractor while9.5 gallons of isopropyl acetate `were being fed into the periphery.Under the inucnce of` centrifugal force, the lighter isopropyl acetatewasdisplaced toward the center by the heavier soap solution and the soapsolution was thus extracted. Theisopropyl-acetate was removed from thecenter containing the non-acids while the soaps essentially free ofnon-acids were removed from the periphery. Analysis of the extractshowed it contained solids which analyzed at least.84.4 percentnon-acids. Conversion of the ratti nate to oil `gave an Ioil `of whichonly 0.8 percent was non-acids. Theextract was later reintroduced intothe periphery of the Podbielniak `extractor while 6 gallons of waterwere being introduced at the center. This amount of water was chosen asit was the amount used to dilute the original skimmings. The washedextract, having been displaced tothe center, was removed while washwater containing the soaps was removed from the periphery. The washwater contained solids which analyzed 13.6 percent non-acids. The washedextract contained solids whichanalyzed by the same method 86.2 percentnon-acids. Analysis `for soap content, however, indicated that thesesolids contained less than 1 percent soaps. The original skimmings whenconverted tooil gave an oil containing 8.1 percent non-acids. Thus amarked reduction was effected in the non-acid content of the oil. At thesame time a non-acid material virtually free from soaps was separated.

Example II A solution of 1 part by weight of black liquor skimmings in 2parts by weight of water was extracted with isopropyl acetate. Thevolume ratio of solvent to soap solution was 1:1. This extraction wasdone in a continuous manner in a three stage mixer-settler type `ofextraction apparatus. A fourth mixer-settler stage was employed forwashing the extract continuously. Crude oil made from the unextractedsoap had an unsaponiable content of 8.5%. Crude oil made from theextracted soap had an unsaponiable content of 2.0%. The extractedmaterial analyzed 88.1% unsaponitiables.

In the preceding examples the soap stock processed was black liquorskimmingsand the solvent employed was 4 isopropyl acetate. However thefollowing solvents were also employed, not only with black liquorskimmings but also with tall oil pitch and cottonseed foots:

N-butyl acetate Iso-butyl acetate Sec-butyl acetate Ethyl acetate Ethylpropionate Amyl acetate Methyl amyl acetate Percent; UnsaponltiablusMaterial Before Ex- After Extraction traction Cottonsced Fonts 2.35 0.E4 Saponined tall oil pitch 28. 9. 90

It should be understood that the process of the present invention can beused equally well on any soap stocks, such as the soap from alkalirefining of vegetable oils, soap made from the pitch that results fromthe distillation of tall oil or fatty acids, or other similar soapstocks con` taining non-acids.

We have found that extremely good extraction is obtained by our processin the temperature range of 80 to F., but higher or lower temperaturesthan the range specified may be used if desired. As heretoforeexplained, there is no upper limit to the dilution of soap stock whichis satisfactory, but economics will, in a practical way, limit theextent of dilution that is desirable. Similarly, there is no knownreason why practically any amount of isopropyl acetate or like solventcould not be used as long as it is enough to exceed the solubility ofsuch solvent in the soap solution chosen. When a soap solution is madefrom one part of tall oil skimmings and one part of water, the minimumamount of isopropyl acetate that can be used at room temperature isabout one volume of isopropyl acetate per volume of soap solution. t

From the foregoing description and accompanying drawing it will beapparent that the process of the present invention is a distinctimprovement over previous solvent separations of the non-acids from soapstocks and is particularly advantageous in the case of aqueous solutionswhere it is possible to extract without the heretofore necessaryaddition of some materials such as alcohols to prevent emulsions.

Since certain changes may be made in carrying out the above processwithout departing from the scope of the invention, it is intended thatall matter contained in the above description shall be interpreted asillustrative and not in a limiting sense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention which, as amatter of language, might be said to fall therebetween.

Having described our invention, what we claim as new and desire tosecure by Letters Patent is:

l. In a method of separating non-acid materials including sterols andhigher alcohols from a product selected fromthe group consisting ofcrude tall oilsoap skimmings and cotton seed foots obtained by alkalinetreatment thereof, the steps which comprise dissolving said product inwater to form a water solution of said soap, extracting said non-acidmaterials from said soap solution with an ester selected from the groupconsisting of ethyl acetate, isopropyl acetate, normal butyl acetate,isobutyl acetate, secondary butyl acetate, amyl acetate, methyl amylacetate, and ethyl propionate to provide a solvent solution of saidnon-acid material, removing residual ester solvent from bcth saidsolvent solution of the non-acid material and the said soap solution byevaporat-4 ing and stripping, acidifyng the solvent-free soap solution 5lation during said extraction step.

References Cited in the le of this patent UNITED STATES PATENTS l02,296,952 Ross et al Sept. 29, 1942 2,315,584 Borglin Apr. 6, 19432,530,810 Christenson et al. Nov. 21, 1950

1. IN A METHOD OF SEPARATING NON-ACID MATERIALS INCLUDING STEROLS ANDHIGHER ALCOHOLS FROM A PRODUCT SELECTED FROM THE GROUP CONSISTIG OFCRUDE TALL OIL SOAP SKIMMINGS AND COTTON SEED FOOTS OBTAINED BY ALKALINETREATMENT THEREOF, THE STEPS WHICH COMPRISE DISSOLVING SAID PRODUCT INWATER TO FORM A WATER SOLUTION OF SAID SOAP, EXTRACTING SAID NON-ACIDMATERIALS FROM SAID SOAP SOLUTION WITH AN ESTER SELECTED FROM THE GROUPCONSISTING OF ETHYL ACETATE, ISOPROPYL ACETATE, NORMAL BUTYL ACETATE,ISOBUTYL ACETATE, SECONDARY BUTYL ACETATE, AMYL ACETATE, METHYL AMYLACETATE, AND ETHYL PROPIONATE TO PROVIDE A SOLVENT SOLUTION OF SAIDNON-ACID MATERIAL, REMOVING RESIDUAL ESTER SOLVENT FROM BOTH SAIDSOLVENT SOLUTION OF THE NON-ACID MATERIAL AND THE SAID SOAP SOLUTION BYEVAPORATING AND STRIPPING, ACIDIFYING THE SOLVENT-FREE SOAP SOLUTION TOLIBERATE SOAP ACIDS THEREFROM AND SEPARATING SAID NONACID MATERIAL.